In recent years there has been great interest in the formation of metal doped polymer films. For example, it has been found that a thin-film coating having a desired color can be readily obtained by introducing metallic particulates into a plasma formed polymer.
Wielonski et al., U.S. Pat. No. 4,422,915 (hereinafter Wielonski), herein incorporated by reference, discloses a method of forming a colored polymeric film-like coating. The film-like coating is formed by depositing a plasma-formed polymer concurrently with particulates. In particular, Wielonski teaches that a plasma-polymerizable material is introduced into an electrical discharge region causing the plasma-formed polymer to be deposited. Concurrent with the formation of the plasma-formed polymer, the particulates are provided.
For providing the particulates, referring now to FIGS. 1, 2 and 3 of Wielonski, a filament resistance heater 29, an inductively heater evaporation source means 36, and an electron beam evaporator 40, respectively, are provided. (Filament resistance heater 29, source means 36 and electron beam evaporator 40 are hereinafter collectively referred to as evaporators.) However, these evaporators have several drawbacks.
One drawback is that each of the evaporators requires dedicated circuitry, e.g. power supplies, for powering the evaporators. Further, to couple the dedicated circuitry with the associated evaporator, one or more vacuum feedthroughs are necessary. Accordingly, the evaporators add complexity, decrease reliability and add cost to the apparatus.
Another drawback is that the evaporators waste the evaporated material and contaminate the process chamber. In particular, referring to Wielonski FIG. 1, evaporation material from filament heater element 29 has a tendency to not only to coat the substrate but also the rest of the apparatus. Thus some (if not most) of the evaporated material from filament heater element 29 ends up coating the inside of the apparatus instead of the substrate thus wasting the evaporation material. This is a particular disadvantage when the evaporation material is expensive, e.g. gold. Further, the buildup of evaporated material on the inside of the apparatus can flake thereby contaminating the apparatus including the substrate. The evaporators of FIGS. 2 and 3 of Wielonski suffer from the same drawbacks.
Accordingly, it is desirable to form a particulate containing polymeric coating using a method that does not require the use of dedicated circuitry to evaporate the particulate and does not waste evaporation material.